1. Field of the Invention
The present invention relates to a stage driving system for controlling a movable stage by the use of a joy stick, for example, such as an X-Y stage driving system in which X-and Y-direction stages can electrically be driven by X- and Y-direction motors, respectively.
2. Description of the Prior Art
There is known a joy stick including an operation lever tiltable in all the directions. Such a joy stick can generate electric output signals corresponding to X- and Y-direction components of a certain direction in which the operation lever is tilted from its neutral position. Upon release, the operation lever will be returned to the neutral position.
The joy stick may be used in an X-Y stage of such a triple-layered structure that a base member carries a Y-direction drive such as a motor, a Y-direction lead screw and an encoder for detecting the position of a Y-direction stage from the rotation of the lead screw, the Y-direction stage being slidably mounted on the base member only in the Y-direction and having a frame threadedly connected with the Y-direction lead screw. The Y-direction stage in turn carries X-direction drive similar to the Y-direction drive, the X-direction drive including an X-direction lead screw threadedly connected with the frame of an X-direction stage which is slidably mounted on the Y-direction stage only in the X-direction. In such an arrangement, the X- and Y-direction drive motors can respectively be energized by electric signals corresponding to the respective X- and Y-direction components obtained from the joy stick.
Systems for controlling the motions of X- and Y-direction stages by the use of a joy stick operation lever are commercially available.
In the prior art systems, the stages cannot satisfactorily be controlled from lower speed to higher speed through the range of lever inclination even if the operation lever is to be tilted from its neutral position under the proportional or exponential relationship, since the magnitude of electric signals depends on the angle of the tilted operation lever.